1. Field of the Invention
The present invention relates to a combustion control device for internal combustion engines, which detects the pressure in a cylinder of an automobile internal combustion engine or the like, and calculates thermal efficiency based on the detected cylinder pressure to control the combustion in the engine.
2. Discussion of Background
There has been known such a combustion control device as disclosed in e.g. Japanese Unexamined Patent Publication No. 72643/1983. The conventional combustion control device uses a cylinder pressure sensor to detect the pressure in a cylinder of the engine to be controlled. The device finds the crank angle at which the detected pressure reaches the maximum value. The device compares the crank angle at that time with the values in a predetermined range to judge whether the engine is being driven at the maximum output or not. Depending on the results of the judgment, the device can suitably adjust the amount of fuel supply (air fuel ratio), ignition timing and the amount of exhaust gas recirculation (EGR) to control the engine at the maximum efficiency and under stable combustion, and also to prevent knocking from occurring.
The conventional internal engine combustion control judges the combustion state by comparing the crank angle having the maximum cylinder pressure with the values in the predetermined range. Change with time of the engine causes the waveform of the cylinder pressure to change, which creates a problem in that the combustion control based on the single factor, i.e. the maximum cylinder pressure, can not always drive the internal engine at the maximum efficiency and under stable combustion.